Magnetic apparatus



Sept. 18, 1928.

C. S. SNAVELY MAGNETI C APPARATUS Filed Oct. 24, 1923 a eelglfXENTOl-T Patented Sept 1 1928.

UNITED STATES PAT ENT oFFicE.

CLARENCE S. SNAVELY, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

MAGNETIC APPARATUS.

Application filed. October 24, 1923. Serial No. 670,446.

My invention relates to magnetic apparatus. g

I will describe one form of apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the acompanying drawing, Fig. 1 is a view showing, in front elevation, one form of magnetic apparatus embodying my invention. Fig. 2 is an end view of the mag netic apparatus illustrated in Fig. 1.

Similar reference characters refer to s1m1- lar parts in both views.

Referring to the drawing, the apparatus comprises an electromagnet A made up of two parallel cores 1 and 2 connected by a back strap 3, which cores are provided, as usual, with windings 15. The core 1 terminates in a pole face 1 of comparatively large area, and core 2 terminates in a pole face 2 of comparatively small area.

The magnet A controls an armature 7 which is provided with a tongue 9 pivotally mounted at point 8 in lugs 6 pro ect1ng from a plate 6. This plate 6 may be supported by any suitable means, not shown 1n the drawing. The thickness of the armature 7 is uniform throughout, but the width of the armature, as viewed in Fig. 2, varies from maximum width opposite the larger pole face 1 to minimum width opposite the pole face 2. In other words, the armature is tapered in substantially the manner shown in Fig. 2. It will be particularly noted that the pole face 1 of greater area is located between the pivotal point 8 and the pole face 2 of smaller area.

The armature .7 may be used to control a load of any desired kind, and, as here shown, this load comprises an arm G WlllCll is biased toward the left and is provided with a hook 11 co-operating with a detent 10 formed on the tongue 9 of armature 7.

I have found thatwhen magnetic apparatus is constructed in the manner described, the torque exerted on the armature 7 due to a given energization of the magnet A, is considerably greater than when the pole faces are of equal area and the armature is of uniform width throughout.

The increased efliciency of the magnet is obtained by varying the pole face areas only, without change of magnetic lines except for their relative densities through the two magnetic air gaps in series. Assuming an electromagnet designed for maximum efliciency, that is properly balanced with regard to the magnetization curve, ampere turn energization and air gap reluctance, with pole faces of equal area, as is the usual case, an increased amount of mechanical work can be done by the armature by changing the pole face areas without altering the total flux value. In changing the pole face areas, they are varied in such ratio that the increase of air gap reluctance of the one farther from the armature pivot is balanced by the decrease in air gap reluctance of the one nearer to the armature pivot. Thus, the total reluctance of the magnetic circuit remains the same as before, and the flux through these air gaps also remains the same. Now, in view of the fact that the pull, when flux remains constant, varies inversely as the area, it is obvious'that the pull on the outer pole piece will be increased, while that on the inner pole piece will be decreased. Hence, due to the difference in lever arms of the two pole pieces, a greater mechanical work can be done by the armature even though all other constants of the magnet remain as before the change. A

Although I have herein shown and described only one form of magnetic apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the' scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. Magnetic apparatus comprising two pole faces of different areas, and a tapered armature having a larger area adjacent the larger pole face and a smaller area adjacent the smaller pole face.

2. Magnetic apparatus comprising two ferent areas, and a flat tapered armature ferent areas, and a fiat tapered pivoted for bridging said pole faces, the widest porarmature for bridging said pole faces the tion of said armature being adjacent the Widest portion of said armature being ad- 10 larger pole face. jacent the larger pole face and between the 5 3. Magnetic apparatus comprising tWo pivoted point and the smaller pole face.

cores connected by a magnetizable back strap In testimony whereof I afiix my signature.

and terminating in spaced polefaces of dif- CLARENCE S. SNAVELY. 

